1. Field of the Invention
The present invention relates to molded plastic products, methods for producing the same, and apparatuses for producing the same.
Recently, it is required, particularly recently, to provide electromagnetic shielding so that electromagnetic noise produced in electronic appliances such as computers, communication equipment and office automation equipment be prevented from radiating outside, or external electromagnetic noise do not invade the equipment. While electromagnetic shielding is easily effected by using a metal body, special consideration must be given when a molded plastic product is used as a body because various requirements including weight, cost and appearance have to be met.
2. Prior Art
FIGS. 1A and 1B are diagrams which explain conventional covers having a shielding capability. FIG. 1A shows a plastic door 11 used as a cover for providing electromagnetic shielding for a large information processing unit. A conductive body 13 formed into a metal plate or a wire netting is fixed to the inner wall of a main unit 12 formed of a plastic material by a fixing means 14 such as a screw so that electromagnetic shielding is effected by the door.
FIG. 1B shows electromagnetic shielding of a relatively small electronic apparatus 15 like a personal computer, wherein a body 16 is made of a plastic material. Since the body 16 is not conductive, parts 17 are accommodated in a case 18 formed of a sheet metal.
However, the door 11 shown in FIG. 1A has a problem in that the number of processes required is great because the conductive body 13 is fixed to the main unit 12 built by molding.
The construction shown in FIG. 1B has a problem in that the number of parts and the production cost are great because the parts 17 are accommodated in the case 18.
In order to eliminate the need to provide the conductive body of FIG. 1A and the case 18 of FIG. 1B, there is proposed electromagnetic shielding by applying conductive paint on the plastic door 11 or the body 16, or by mixing metal filler in the material forming the door or the body so as to achieve conductivity. However, such an approach has a problem in that recycling of the material is difficult and the production cost is high.